Seedling growth enhancing device

ABSTRACT

A seedling growth-enhancing device is disclosed, consisting of a circular tube formed from flexible, non-opaque thermoplastic material having a slit formed over its length. The tube is of sufficient size as to substantially enclose the seedling, and the plastic material is inherently resilient so that the device is normally biased into its tubular configuration. The opposed edges of the slit are fastened at the top and bottom to permit the edges to be resiliently spread at an intermediate point to permit access to the seedling for maintenance. Also disclosed are an H-clip for releasably fastening the opposed edges and a wire hanger for suspending the circular tube from an overhead suspension wire.

This application is a continuation of application Serial No. 08/936,901,filed Sep. 25, 1997 now U.S. Pat. 6,138,404 which application(s) areincorporated herein by reference.

The invention is directed to devices for enhancing the growth and formof plant seedlings.

Within the past two decades, plant seedling growth enhancers have beendeveloped and used to assist newly planted seedlings to survive and growat an enhanced rate and improved form during the early stages afterplanting. Seedling growth enhancers have found their greatestapplication to date in the forestry industry where they are installed atthe time the seedling is planted and typically remain in place for aperiod of 5-7 years.

Seedling growth enhancers are commonly referred to by the misnomer“treeshelter”, which suggests that the device functions to protect or sheltermature trees. However, it is known in the technology to which thesedevices pertain that their primary function is to not only protectimmature seedlings but, more importantly, to create a micro-environmentin which the seedling may flourish in much the same way as a greenhouseenhances the growth of plant seedlings.

Typically, such seedling growth enhancers take the form of a tube ofthermoplastic that typically is translucent with a diameter sufficientto encompass the seedling during the period of use and a length thattypically is less than the seedling at the time of planting. An exampleis shown in U.S. Pat. No. 4,899,486 issued to Graham F. Hurlstone onFeb. 13, 1990.

The thermoplastic material used in the formation of tree seedling growthenhancers is often chosen to be degradable when exposed to ultravioletlight. The degrading effect takes place over a time that correspondsgenerally to the period during which protection and growth enhancementis necessary. Thus, as the tree seedling matures over a number of years,the device progressively degrades in the presence of ultraviolet lightand ultimately disintegrates when its function is no longer necessary.

We have found that the principle of seedling growth enhancers may beadvantageously applied to other types of seedlings, such as grapevineseedlings which are continuously planted in the grape industry tomaintain a necessary level of grape production. If this growth can beenhanced to the point that quality grape production begins at an earlierpoint in time, this is economically beneficial to the vineyard owner.

Seedling growth enhancers (also known as grow tubes) are advantageouslyused in connection with grape seedlings. One of the primary benefits isto guide the vine upward in its growth without the need for staking.Without training seedlings to grow upwardly in some manner, they willgrow at will along the ground. Grow tubes train the vine to grow upwardin a position to be more productive.

Grow tubes also enhance the growth of grape vines by capturing moistureand recycling the moisture as it condenses from vapor on the inner tubesurface. Grow tubes also protect the grape vines from herbicides byacting as a barrier or shield to the seedling.

However, conventional grow tubes create a problem insofar that seedlingmaintenance is concerned because they are in essence permanentlyinstalled, and access to the seedling is not possible without removingthe plastic tube. Access to the seedling is important because of thepossibility of choking weeds, as well as to prune the seedling to ensurethat it has only a primary leader during its initial growth stage. Inaddition, access is necessary to determine whether the seedling isexposed to disease or insect infestation. If access cannot be gained tothe grape seedling, its growth may be inhibited or improper for any ofthese reasons.

These problems have been solved by producing a grow tube having alongitudinal slit over its length together with means for fasteningadjacent edges of the slit at the top and/or bottom of the tube. Accessto the seedling is gained by spreading the slit at an intermediate pointof the tube.

It is important in this regard that, when the opposed tube edges arespread to gain access to the seedling and then released, the accessopening is self-closing and the tube returned to its tubular form. Thisfunction is not possible if, for example, the tube is formed by simplyrolling a flattened rectangular sheet of plastic into a tube. With sucha construction, the fastening means holds the opposed edges together butthe tendency is for the edges to pull apart. Consequently, the accessopening is normally open and the integrity of the tube and thegrowth-enhancing function are lost.

We have found that the access function is best obtained by forming thedevice as a continuous plastic tube (e.g., by extrusion) and thenslitting the tube longitudinally. In this manner, the tube has inherentresiliency and hence a bias to return to its tubular form after havingbeen spread apart. By fastening the opposed top and bottom edges, accessmay be gained by spreading the opposed edges at an intermediate pointand simply releasing the edges after the pruning and dressing functionshave been completed.

However, we have also found that the material from which seedling growthenhancers are conventionally made produces a springiness that, inessence, overbiases the tube edges together, which makes them difficultto spread apart and, accordingly, difficult to use. Specifically, thisoverspringiness requires use of two hands to spread the tube and to holdit in the spread-apart position, which makes it quite difficult tomaneuver the pruning tool into the slit to perform the pruning tasks.Testing has shown that conventional seedling growth enhancersmanufactured from polyethylene require at least about 1.5 pounds offorce to spread the tube edges a distance of three inches.

In order to operate properly and efficiently, we have found that theamount of force necessary to spread the tube edges three inches apart beno more than about 0.5 pounds. Our testing of various materialsindicates that low-density polyolefins (such as low density polyethyleneor low density polypropylene) are a suitable material to render thisresult.

Producing the seedling growth enhancer (or grow tube) in this manner isalso advantageous because it enables the device to be reused after theprotected seedling has matured to the point that protection is no longernecessary. This is accomplished by releasing the top and/or bottomfastening means, which enables the tube to be spread over its length andhence removed from the grapevine or other seedling. The tube can then bereused by placing it around a new seedling, or stored for further use bynesting a number of the resilient tubes together.

It is conventional to connect the overlapping edges of the grow tube bystaples. Stapling is an economic approach to fastening, although astapling tool is required in the field at the time the grow tube isplaced, and it requires some degree of strength and dexterity toproperly affix the staples. An alternative embodiment for fasteningadjacent edges of the grow tube together takes the form of a uniqueslidable clip having a H configuration in cross-section with a lengththat corresponds to the length of the grow tube. The opposed legs of theH-shaped clip are biased together and the distance therebetween, atleast at the entry point, is less than that of the thickness of thesheet material from which the grow tube is manufactured. This enables auser to connect the opposed edges of the grow tube either by forcingeach edge between the spaced legs of the H-clip, or sliding the H-cliplongitudinally over the adjacent edges. In either manner, the edges arequickly and easily joined together without the use of any type of tool.Use of the H-clip is also beneficial in maintaining the tube diameteruniform over its length.

Further, the edges of the grow tube may be easily spread apart byraising the H-clip a sufficient amount to permit edge spreading andaccess. Also, the grow tube may be reused by removing the H-clip,spreading the edges to the point that the tube can be removed from theseedling, and subsequently rejoined for use on a new seedling.

One of the preferred embodiments of the invention is specificallyintended to be placed over the seedling and to be supported by moundingearth around the base of the grow tube. An alternative embodimentutilizes an overhead suspension wire, known in the vineyard industry asa cordon or fruiting wire, and includes a unique hanger that interfaceswith the top of the grow tube and wraps around the suspension wire. Inthis manner, the grow tube is firmly held in place from above as well assupported by the ground below.

The inventive grow tube is highly advantageous because it provides easyaccess to the grape seedling for weed removal, pruning and determiningthe vitality of the plant. As a consequence, growth of the seedling isenhanced, causing it to mature more quickly and to produce grapes at anearlier point in time.

The various functions and features of the invention will be more fullyappreciated from the specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a seedling growth enhancer embodying theinvention which utilizes a removable joinder clip and a hanger foroverhead suspension;

FIG. 2 is a fragmentary view of a seedling growth enhancer beinginstalled in the ground;

FIG. 3 is a front elevational view of the installed seedling growthenhancer spread to permit pruning;

FIG. 4 is an enlarged fragmentary perspective view of the seedlinggrowth enhancer as secured to an anchoring stake;

FIG. 5 is a perspective view of an improved fastening means for joiningthe opposed edges of the seedling growth enhancer;

FIG. 6 is an end view of the fastening means with the opposed edges ofthe seedling growth enhancer prior to fastening;

FIG. 7 is a view similar to FIG. 6 with the opposed edges of theseedling growth enhancer fastened by the fastening means;

FIGS. 8-12 are fragmentary front elevational views of the seedlinggrowth enhancer and hanger, showing through progressive steps how thehanger is connected to an overhead suspension wire.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With initial reference to FIGS. 1-4, a seedling growth enhancer or growtube embodying the invention is represented generally by the numeral 11.Device 11 takes the form of a length of tubing 12 that is extruded froma thermoplastic material described more fully below. Preferably, thethermoplastic composition resists ultraviolet light and is capable ofbeing used and reused over a significant period of time.

With reference to FIGS. 6 and 7, the plastic tubing 12 is preferably oftwin wall construction, having an inner wall 13 and a spaced parallelouter wall 14 interconnected by a plurality of transverse wall spacers15. The overall thickness of the twin wall is on the order of 40-100mils To enhance photosynthesis and growth, the thermoplastic materialmust be capable of transmitting light rays R (FIG. 7), and thetwin-walled tube is therefore translucent or transparent (i.e.,non-opaque).

As best shown in FIGS. 2, 6 and 7, a longitudinal slit 16 is formed inplastic tubing 12 from top to bottom. It is important that, even withlongitudinal slit 16, tubing 12 inherently remains in a tubular state;i.e., it has inherent resilience or“memory” that causes it to return tothis tubular state even though the longitudinal edges defining slit 16are set apart. This is most effectively accomplished by extruding theplastic tubing 12 into tubular form, cutting it to required lengths andthen cutting the longitudinal slit 16. Other means or structures may beused provided the tubing 12 has the tendency to return to its normaltubular form as shown in FIG. 1.

With continued reference to FIGS. 3 and 4, the grow tube 11 ispreferably fastened at both the top and bottom of the slit 16 by afastener such as a staple 17, although it is possible to use only asingle staple 17 at either the top or the bottom.

With reference to FIG. 3, grow tube 11 may be installed by spreading itaround the seedling and then mounding earth around the bottom of thetubing 12 to hold it in place. It is also possible to force the loweredge of tubing 12 into the earth around the seedling if the earth issufficiently soft.

As shown in FIG. 4, it is also possible to drive an anchoring stake 18into the ground adjacent grow tube 11. A pair of apertures 19 are formedat both the lower and upper ends of tubing 12 permitting it to be tiedto the stake 18 with string 21. The placement of apertures 19 at bothends enables the grow tube 11 to be tied to the stake at spaced pointsfor greater stability, and also enables the grow tube 11 to be used bothright side up and upside down.

With reference to FIG. 3, grow tube 11 is shown in connection with agrapevine seedling S which has grown to the point that its upper end(also known as the primary leader) projects beyond the top of tubing 12.During such growth, a number of intermediate or secondary leaders L havegrown which require pruning. With conventional seedling growthenhancers, pruning would not be possible without removing the deviceitself. However, the inventive grow tube 11 permits access for pruningby spreading the opposed longitudinal edges of slit 16 at anintermediate point, holding the edges apart with one hand and pruningthe secondary leaders L with the other. After the pruning has beencompleted, release of the edges causes the tubing 12 to return to itstubular form as shown in FIGS. 1 and 2. In this regard, it has beenfound that forming tubing 12 from relatively rigid material, such ashigh density polyethylene, provides good rigidity and stability to thegrow tube 11, but also makes the opposed edges at slit 16 difficult tospread with one hand. If both hands are required, it is difficult if notimpossible to have a free hand necessary to insert the pruning toolthrough the access opening.

The material to be used must, therefore, be of sufficient rigidity as toenable the grow tube 11 to protectively stand and surround the seedlingS, but also sufficiently supple as to permit the slit 16 to be spreadand maintained as an access opening with a single hand. We have foundthat the force necessary to spread slit 16 should not be more than about0.5 pounds. With the twin-wall construction shown, extruding tubing 12from low-density polyethylene suitably provides this function.

Although staples 17 perform satisfactorily in holding the top and bottomoverlapped edges of tubing 12 together, they require having a manualstapler in the field, which is a disadvantage. Further, if the grow tube11 is to be reused after the seedling S grows to a sufficient size, thestaples must be removed before the tubing 12 can be spread apart andremoved. Removing the staples 17 is also problematic because it requiresa staple remover, pliers, or the like and requires time to perform thisremoving task. While the time is not overly significant with regard to asingle grow tube 11, it must be kept in mind that large vineyards usethousands of the grow tubes and each repetitive task increases both thetime and cost of maintenance.

FIGS. 1 and 5-7 disclose a fastening device 22 that is quickly andeasily used without the need for a tool, and which firmly but releasablyholds the opposed edges of slit 16 together. The fastening device 22 hasa generally H-shaped transverse cross-section and is defined by aslightly curved leg 23, a slightly curved leg 24, and an intermediateconnecting leg 25. The legs 23, 24 together define opposed leg pairs ateach side of the device. Leg 23 is shorter than leg 24, and its extremeends curve more aggressively toward leg 24 to define opposed gaps 26between the opposed leg pairs, the size of which is less than thethickness of twin-wall tubing 12. H-clip 22 is preferably extruded froma thermoplastic such as polyvinylchloride or polyethylene and the legs23, 24 may therefore be resiliently spread apart to permit entry of theedge of tubing 12 after which it is held frictionally by the inwardspring bias of the leg pair.

The entry of each opposed edge of tubing 12 into the H-clip 22 is guidedinto the gap by the segment of leg 24 which extends laterally beyond theends of leg 23. As particularly shown in FIG. 7, the aggressivecurvature of the extreme ends of leg 23 causes it to bite into the outerwall of the twin-wall tubing 12 and cause it to be depressed betweenadjacent spacers 15. This improves the gripping power of the H-clip 22,ensuring that the opposed edges of tubing 12 will be held in fixedrelation during seedling growth.

H-clip 22 may be used either as a single length that generallycorresponds to the length of tubing 12, or as a shorter individual clipas shown in FIG. 5. In either case, access to the seedling S may beeasily gained. If a single length is used, access to the seedling S isgained by sliding the clip upward until a sufficient length of slit 16is exposed to permit the opposed tubing edges to be spread apart. If theshort clip is used, one is placed at the top and one at the bottom oftube 12 in the same position as the staples earlier described, and slit16 is spread at an intermediate point without removal of either clip 22.In either case, the H-clip 22 can be easily removed, either by pullingit longitudinally or by gripping the opposed sides of tubing 12 andpulling them from the clip 22, which enables the removal of grow tube 11from the grown seedling S for reuse.

Grow tubes 11 may be conventionally placed as shown in FIGS. 2 and 4;i.e., by mounting earth at the base of the grow tube 11 and stabilizingit with a stake 18. However, it is also conventional in vineyards to useoverhead suspension wires that extend along rows of grape seedlings,such as suspension wire 27 as shown in FIG. 1. This enables the use of ahanger 28 which fits over the suspension wire 27 and frictionallyinterlocks with tubing 12.

Hanger 28 is formed from a length of ductile wire that is bent into aspecific configuration. As shown in FIG. 1, hanger 28 has a primary leg29 that is straight in the preferred embodiment but which is bent at arelatively low obtuse angle to define a short angled leg 31. A pair ofsubstantially vertically spaced apertures 32 are formed through tubing12 in its upper end in the side opposite the slit 16. The angled leg 31enables the lower end of hanger 28 to be through the upper aperture 32from the inside of tubing 12, and then to be threaded back through thelower aperture 32 into the position shown in FIG. 1. This is permittedby the flexibility of the ductile wire of hanger 28 as well as theresilience of the twin-walled tubing 12. As the result, the main leg 29is frictionally held in the position shown and this position may beadjusted to reconcile the distance between the top of grow tube 11 andthe suspension wire 27.

The upper end of hanger 28 is bent to define a hooking portion definedby a first leg 33 that is bent at 90° relative to main leg 29, a secondleg 34 that is also 90° relative to main leg 29 but bent at an obtuseangle relative to first leg 33, and third leg 35 that is bent 90° to beparallel with main leg 29.

FIGS. 8-12 show how the hanger 28 is used in suspending the grow tube 11from the Cordon wire 27. With reference to FIG. 8, the hanger 28 isinitially placed with the leg 33 overlying Cordon wire 27. In FIG. 9,the leg 34 is grasped, either by hand or through the use of a tool T.With reference to FIG. 10 tool T is drawn downward until the leg 34 andleg or hook 35 lie below the Cordon wire as shown in FIG. 11. Next, asshown in FIGS. 11 and 12, tool T engages leg 34 and draws it upwardlyand around Cordon wire 27. As shown in FIG. 12, tool T is now rotateddownward without disengaging it from leg 34, and leg 34 is pushed up andover Cordon wire until hook 35 engages Cordon wire 27. The finalposition of hanger 28 is shown in FIG. 1, with Cordon wire 27 threadedaround legs 33, 34 and hook 35 of hanger 28. The obtuse angle subtendedbetween legs 33, 34 provided a pivot point during this threadingprocedure.

With grow tube 11 firmly suspended from Cordon wire 27, its positionrelative to hanger 28 may now be adjusted so that the bottom of tube 12rests on the ground below. It is strongly preferable that, with the tube12 so adjusted, loose earth be mounted around the base of the tube 12 sothat it is supported from the bottom as well as the top.

It will be appreciated that hanger 28 may be quickly and easily insertedinto the apertures 32 of a grow tube 11, followed by hooking the hanger28 over and threading it around Cordon wire 27. Properly installed, growtube 11 is firmly and stably supported at its upper end by Cordon wire27 and at its lower end by the mounted earth. With slit 16 in directopposition to hanger 28 and with the use of either staples or clips 22,access to the seedling 16 may be readily gained in much the same way asshown in FIG. 3.

We claim:
 1. A seedling growth-enhancing device comprising: a seedlingenclosure member of tubular configuration and of predeterminedtransverse dimension and length as to at least partially encompass aplanted seedling, the enclosure member having a top end and a bottomend, the enclosure member being made from flexible, non-opaque materialand having a slit formed over its length to define adjacent longitudinaledges, said flexible, non-opaque material being inherently resilient sothat the enclosure member is normally biased into said tubularconfiguration; means for fastening said adjacent longitudinal edgestogether proximate at least one of the top end and bottom end of thetubular enclosure member; the fastening means being constructed anddisposed to permit said longitudinal edges to be spread apart at anintermediate point on said enclosure member to permit access to theinterior thereof; and the non-opaque material of said enclosure memberbeing sufficiently flexible and supple as to permit said longitudinaledges to be spread apart and maintained apart with a force applied witha user's one hand so as to enable access to a seedling within saidenclosure member with a user's other hand, and being sufficientlyresilient as to cause said longitudinal edges to close said accessopening when said force is removed.